A few days ago I noticed I had slight pain on my butt, and assumed it was a bruise. When I looked, it appeared to have a small pimple on it. Over the last 3 days, it has grown much bigger, but I don't know what it is. I've tried washing and exfoliating the spot, using Stridex, and soaking in hot water, but it won't go down. 

It's nowhere near the tailbone or rectum. I'm not sure if it's a pimple/zit, a cyst, or an abcess. It might even be a bug bite. 

I maintain perfect hygiene, and I don't work out, but I live in a hot desert so I do sweat sometimes. I also sit a lot at the computer. I am 17 and female. 

I also have swollen lymph nodes around the groin, and I'm certain it's related to the lump. 

Please do not post about having a similar issues that are in no way like my issue. I'm posting here for help and advice, not empathy. 

Image of the lump: https://i.imgur.com/LfJp9AGh.jpg

It is very big and painful. I can not sit or walk comfortably.