One of the vains on my penis feels hard is that normal?

No. Penile veins should be soft. The hardness could be due to thrombosis of the vein. This iss probably not serious unless you also have pain or swelling in your legs which would suggest something more serious and requires urgent medical consultation.
Thrombosis . This might represent a thrombosis of the dorsal penile vein. This is a benign condition occuring because of the trauma of intercourse and treated with low dose Aspirin (81 mg) until it resolves. Usually takes several weeks to get better but resolves completely. Please have this evaluated by your medical doctor or urologist to be sure the condition is not something more serious.