What Causes Lump On Shaft Leading To Painful Erections And No Masturbation?

i have had a lump in the shaft of my penis and painfull erections making sex and masturbation impossible for 18 months. Peronies Disease has been diagnosed but is it normal for the active phase to last this long and how much longer could it last. I have had an Ultrasound which was when the diagnosis was made but recently had an MRI which was clear.