How Long Until Restylane Bumps on Lip Smooth Out?

You may feel the "bumps" from Restylane injections in the lips for a considerable time. However, any external visible bumpiness goes away rather quickly as the body re-balances the water content between your tissues and the hyaluronic gel.
But why do you feel bumps on the inner lip? The lip tissue is very much like sponge, with different sized "cells" so the way your lip accepts the Restylane will determine how much - or how little - you feel in the inner lip.
The lining inside the lip is very thin, and there's a good chance you would have felt natural bumps had you taken the time to explore with your tongue before your injections. Certainly after the injection, the increased volume in the various cell compartments will be something you will feel as the tongue is acutely sensitive to changes inside the mouth.
Restylane and Juvederm both "pull" water from the skin and this is how the plumping effect is maintained. Good injection technique will prevent any long term "bumps" that are visible externally.

Great question and be patient. The bumps and firmness you may be feeling are likely from the injection and not the actual product. They are probably mucosal hematomas or bruising in the lip. It may take almost 2 weeks for them to go away, and if not resolved at that time it may represent some product which is temporary and will go away over time. Sometimes massage can help as well if really bothersome after a month you could try to have it dissolved with a hyaluronidase injection.
Fat injections to the lips are great, though it too can be temporary and uneven. The hyaluronic acid gels are a great introduction to lip augmentation, however there is no great permanent option that is not frought with problems. You may want to stick with gels for now and see what you like and what you dont and then make the decision on fat grafting.