Under the skin pimple ???? Pleeeease hellllpppp :)?

I usually get a little breakout during the time aunt flow visits... So my dermatologist put me on epiduo and it really does work.. I have clear skin right now but on my chin.. I feel an under the skin pimple.. You CANNOT see it.. It's not red... It jus really hurts... I just took a shower and cleaned my face with cetaphil, then I put hot compresss on it.. & then put epiduo on my whole face like usual... If I put toothepaste on it tonight and sleep with it on.. It should stop the pimple in it's track so it doesn't rise and become hideous ?