Lump on leg

So, yesterday, I noticed a strange divot on my leg. The picture shows it and on my other leg that is just a straight line, no indent. The divot is followed by a large hard lump. About the size of an egg. It's tender, a little painful when moving but not bad. There is no discoloration.

I'm 15 weeks pregnant. Anyone had this before or have a guess of what it is or whether it's concerning? Guessing it's just a deposit of some sort. Thought I'd check. Thank you!!!