What happens if I accidently use pink eye medicine while still having my contacts on? Can I still use the contacts?

Probably little. A good general rule is that if your eyes become red to any degree, you should remove your contacts. The addition of 'pink eye " medication, whatever that might be, probably makes no difference one way or another. You should remove the contacts, clean them thoroughly and wait for the redness to go away. Then you can rewear the contacts.