Can I get rid of the knot in my lip after a motorcycle accident with a face injury?

Likely. Depends on when - how long ago? How big penetrated? No foreign body- gravel etc likely scar or absorbing hematoma if early, or stitches if used. Revision of the scar can be very effective!
Yes. You can often get scar, hematomas or mucoceles (collection of minor salivary glands that herniate) after traumatic injury. Often they will improve or resolve with tincture of time. If it has been present for over 6 months it will most likely not go away on its own and you may want to see your local otolaryngologist (ENT) or plastic surgeon for surgical options.