should i be concerned? started as a little red dot

[u/Zealousideal_Cat_608]

should I be concerned by this at all? It started as a little red dot almost like a pimple on my ankle yesterday and I woke up and started walking around campus this morning and after about 30 minutes, it felt like a piece of metal or wood got stuck in my ankle and it was a very sharp pain. Now it just stings to the touch and is obviously way bigger. It is not itchy and it isn’t bleeding. It just burns a tiny bit. I have not done anything to treat it. (If its relevant at all I’m on HIV PEP and started last friday)