A few doors down, Sugar Heaven needs to dispose of $20,000 worth of melted chocolate, sanitize candy bins, and collect phones, purses, and other baggage left in the aftermath of Monday’s twin explosions.

And at Marathon Sports, president Colin Peddie said the task of repairing windows and cleaning carpets will be the easiest part of reopening at 671 Boylston St., where employees just days ago were wrapping tourniquets around injured spectators.

“We still have to get together as a company and discuss what happened and come to grips with it,” Peddie said. “Everyone handles those emotions differently. We have to make sure we’re listening to each other and start to rebuild.”

Peddie’s store is among more than 400 businesses in the Back Bay that have been unable to reopen because the section of Boylston Street around the Marathon bombings is still a closed-off crime scene. The companies are worrying about spoiled food and rodents, merchandise left outside in the recent rains and the state of their employees, while struggling to assess damages and prepare insurance claims without having seen what shape their properties are in.

Beyond that are more traumatic challenges: Employees are grappling with gruesome memories; some restaurants, such as Forum, have injured workers; and there are visual reminders like bloodstains and blown-out storefronts from the blasts that killed three people and injured 282 others near the finish line on Boylston Street.

“I have never seen such a large group of retail employers being affected for this long of a period in Massachusetts. The economic losses are hard to measure but certainly were in the hundreds of millions regionwide,” said Jon Hurst, president of the Retailers Association of Massachusetts. “For the directly affected Copley and Newbury Street region, which is so dependent upon retail and restaurants, the collective lost business and wages must already be in the tens of millions. Some of this will never be recovered.”

As of Monday afternoon, hundreds of Back Bay businesses had registered with the city to receive updates on the reopening of Boylston Street and information about assistance available to those struggling to recover from the bombings.

Sheila Dillon, who is coordinating the city’s response, said Boston officials are processing a massive wave of inquiries. Merchants want to know when they can get back into their buildings; some have cash flow problems, others are worried about coffee pots and ovens left on, carpets stained from blood and other debris.

“We’ve been asked about the total financial impact, and at this point we really don’t know,” said Dillon. “Certainly this is a very busy time of year for a lot of these businesses and restaurants. For many of them, Marathon Monday is their biggest day. They have lost a lot of revenue.”

City Councilor Mike Ross, whose district covers the Back Bay, said he is lobbying federal officials to make disaster assistance available to struggling companies — especially after a difficult year that involved closures from snowstorms and NStar outages. Ross is urging diners, shoppers, and other businesses to patronize Boylston Street businesses in the coming weeks and months.

“It’s not just the businesses themselves feeling this, it’s also their employees,” Ross said. “If you take 10 of these restaurants, you are talking about 1,000 people who rely on these businesses being open to earn their income.”

The FBI returned Boylston Street to the city’s control at 5 p.m. Monday, but the blocks between Berkeley and Hereford will remain closed until city officials clean up the area.

Mayor Thomas M. Menino has enacted a five-step reopening process that includes decontamination, structural assessments of buildings, debris removal, and counseling for returning businesses. Officials said it could be another day or two before the street is reopened to regular traffic.

And for some businesses, the process will be much longer, as they will need to repair windows, scour floors, get damage assessments, and restock.

There is a long to-do list at the Charlesmark Hotel, where operating partner Mark Hagopian sat on the outdoor patio about 35 feet away from the second explosion last Monday.