Why is one part of my scalp tender to touch? only a light touch hurts if, not a pressing one so i think it's only my scalp that's affected

Shingles?: If this is new (a day or two), and if the tender area is only on one side of your scalp (i.e. tenderness stops at the midline and doesn't extend to the other side), be on the alert for red bumps that would soon turn to blisters and sores. It could be shingles, i.e. a localized recurrence of the chickenpox virus (if you weren't vaccinated and had chickenpox as a child.) See MD if any doubt.