Woke up with small blister on bottom lip doesn't hurt?

Possibly bit lip: You may have inadvertently bit your tongue in the night. Normally, it resolves rather fast. If it happens often, possibly a dentist can file down any sharp edge of the front teeth/tooth that are contributing to your problem.

Very well: could be a cold sore, classically caused by the herpes virus. Be careful as this may be contagious, it is truly from a herpes virus; avoid kissing anyone until the lesion is healed. You can consider trying an over the counter remedy like Abreva(which is applied to the lesion 5X/day). But you may review this with your doctor, as for the right person, prescription antivirals can be used too.