Generally speaking, time with all and only good credit is the cure.
But:
Get a copy of your credit report from all three vendors (TransUnion, Equifax and Experian). Study them carefully, and if anything is in error, dispute it.
They are supposed to correct or remove the entry within 30 days.
Here's how to get ahold of each one. You can do the ordering, and if necessary, disputing, over the phone or online nowadays.
TransUnion: 800-888-4213 or
online
Equifax: 800-685-1111 or
online
Experian: 888 397 3742 or
online