What Causes Heat Boils On Penile Shaft?

Hi, I have problem on my penis shaft.. some sort of an heat boils but its harder and couldn t remove it like normal heat boils . Before it was few now it has spreaded. It gives me too much of irritation and itching. Please do let me know what it might be. I hv this problem from past 7years. I neglected it before but now worried about it.