Can someone tell me what this is?

We've had our Leo, Ecko, for about 2.5-3 years. And by what I would call her left armpit she's always had (what looks to me anyways) a boil looking thing. It doesn't seem to be filled with fluid and it doesn't seem to bother her. Tonight when I was handling her tho, it seems to be a bit larger than I remember it being.

She lives alone in a 15 gallon tank. Eats mealworms and crickets and lets you know when she's hungry. (by staring intently at the cricket container)
Her day time temps are about 90 on the warm side. And 85 at night. Her cool end is about degrees cooler at all times.

She has a heat pad, and her light has a dimmer switch so I can adjust it the few times cool weather comes to Houston.
I am enclosing some pics of her boil, bubble, lump, thing, etc.......... That I took tonight. And her set up.
The last picture (I think. There should be a green in the background) is from late 2012/early 2013. I never really took a lot of pics of her when we first got her, but she's pretty much always had the lump.
Any ideas as to what it is?

It's totally normal. Most folks say it's a calcium deposit but I'm not sure that's 100% true. Whatever it is lots of healthy leopard geckos have them

My gecko has this as well! So strange I clicked on this as I just noticed it on both sides this morning.

Ok, I just wanted to be sure. I remember for my first couple months of seeing it, I was obsessively checking her cage for hot spots cuz it made me think of a blister... Obviously I never found any, and it never bothered her so I've just monitored it this whole time. Do you know if it only shows up on one side? Or should it be on both?

My gecko Leopold has them on both sides. Granted right now he has some dry skin on his back, those have always been there and have never caused me a problem.