So under my left arm in my arm pit i have a circular sore where there is no skin it hurts at the touch and ive recently have changed deodorant not sure if its the cause. armpits were over perspirating but calmed down havent used any in a week?

This could certainly be caused by a different deodorant. This deodorant should not be used any more. If the area does not heal, then see your doctor to have it evaluated and treated, if needed. Good luck!

Agree with Dr Ferranti. In addition to stopping the deodorant and observing, you can apply bacitracin (an antibiotic ointment, which is over the counter) to the area 2-3x/day. Also, as some people of any gender shave underarms, I would recommend not doing that while the sore is there. And, as Dr Ferranti said, see your doctor if worsening or not improving.

I agree with the previous recommendations. There's no area that has no skin. Since you have only one tender lesion, it could be a blocked pore or ingrown hair that is inflamed. Apply warm water compresses, pat dry and apply the antibacterial ointment.