 [ Symptoms ] i donated plasma the other day my vein is now hard and hurts and i am getting bad headaches [ Disease ] the symptoms appear to be due to superficial thrombophlebitis that is inflammation of the wall of the vein with formation of a clot you should consult a physician and get a clinical examination done if required investigations like doppler and cbc can be advised as of now do warm compresses over the area apply analgesic gels and take anti inflammatory painkiller like ibuprofen hope this helps