How long does it take to fix your credit history?

My boyfriend went only 162.00 in debt with bank of america but hasnt had the funds lately to pay it back right away.it was fwd to a debt collection agency. its july and we want to move in october. if he pays it right away, directly to bank of america, will his credit go back to to the way it was. Im concerned about when the next place we move does a credit check. hes never been in debt before that.