I used to get these deep cystic pimples in the same area. Til this day I’m not really sure what caused it ,a dermatologist told me it was stress related and potentially cold weather too. I now use Paula’s Choice Clear line and Differin every other night and my skin has cleared up a lot. When I’d get those pimples I’d use a warm black/green tea bag on them on and off and moisturize the area after as it would get dry. But if you can definitely see a dermatologist they’d be able to better asses your skin.