I have a large, swollen, under the skin pimples, what to do?

See dermatologist: You may have developed an abscess so I would see a dermatologist about this

Diagnosis needed: If it's a single bump, it could be an infected cyst or an abscess or a couple of other things. It won't hurt to apply warm compresses as often as you can manage to bring infection to a head, but you should see someone (generalist) because most cysts and abscesses need to be drained ultimately and cause it could be something else. So make the appointment. You can always cancel if it disappears.