24 hours after lip fillers. Is this a lump instead of swelling? (Photo)

Totally see and understand your concerns. 
1. If you feel filler knot then its filler - I'm betting you already did this.
2. More likely that its localized swelling from some blood/bruise you cannot see yet.
3. But it can be both!
You should feel free to have doc look at it but you can also safely wait few more days and see what it looks like. If you dont feel a lump then good chance its localized swelling from bruise that may take 5 to 7 days or more to resolve.
Good luck and let us know how it turns out - even better post a picture in 7-10 days. We are all here on RealSelf to learn!

Hello,
Usually it may take as long as 1-2 weeks for product to settle, at 24 hours it is hard to tell what you need.  Be patient and get injections with products that are reliable. Hope that helps, Dr Violetta Mailyan.