It looks like a carbuncle, which is a painful, red lump caused by a deeper skin infection, usually due to bacteria.
Next Steps
Applying warm compresses (a clean cloth soaked in warm water) 3–4 times a day can help it come to a head and drain naturally.
Avoid squeezing or pricking it, as that can worsen the infection.
As it looks like moderate in size, you may need antibiotics or sometimes a small drainage procedure by a doctor to remove the pus.
Health Tips
Let me know if you have fever, increasing pain, or spreading redness — that means you should see a doctor soon for drainage and antibiotics.