I am experiencing scalp tenderness to touch, scalp itching and rash on scalp.

Scalp tenderness.: see a doctor. could be shingles, infection . will have to be examined.

Dermatitis: Suggest consult as there are a few inflammatory scalp conditions. Or a virtual consult where you can share pictures. Commonest cause in your age would be irritant dermatitis often due to soaps/shampoos

See below: Probably seborrheic dermatitis- use a tar shampoo and an otc cortisone solution