My husband's tooth is loose a little tiny bit. Will it fall out or recover if we leave it alone?

More info needed. We would need to know why the tooth was loose. Underlying peridontitis? Trauma? Non-vital nerve? Without this info, can't possibly tell why the tooth is loose. In general, dental problems do not resolve, they only get worse without treatment. It would be smart to have your husband evaluated by a local dentist.