It looks like contact dermatitis to the shampoo and drying of the penis skin as a result. The mainstay of management is liberal use of moisturizers after washing with luke warm water. Soap should be used minimally. Moisturizers should be reapplied liberally during the day. You can also use a topical cortisone (steroid) cream or ointment and if the symptoms persist then get an evaluation done from a dermatologist.
I hope it helps. Take care and regards.
Oh almost forgot if theres something wrong is there anything i can do to help it get back to its old self?