I can't see anything in the picture, sorry.
How long has it been there?
It's probably nothing but anchor worm does start out as a bump so keep an eye on it. If it's anchor worm you'll be able to see the worm with the naked eye once it starts to come out.
For now just continue to watch it and pay extra attention to water quality over the next month and see if that has any effect. Siphon the gravel, water changes, test the water, don't overfeed, etc