Peyronie's Disease is not uncommon when on hormone therapy, thought to be due to lack of erections, but can also be caused by scarring at injection sites with Caverject, Invicorp, Viridal. Started happening to me due to hormone therapy although not painful, and a urologist friend advised more use of pump. A month of 2x15mins per day fixed it.
Your case may be different because the pain suggests the formation of plaques (scar tissue), which you might be able to feel when soft. I didn't have that. I don't know if the pump strategy is also appropriate in that case. You want to get seen ASAP because there are some medications which can be tried to stop it getting worse, but it's not trivial to repair.
If you have the SOMAerect pump, there are some additional tubes available to put inside it for correcting Peyronie's (which you should be able to get on the NHS), although I don't have those. You can buy the pump with them as the SOMAcorrect. Again, it may depend on why it's happening if that's a good idea or not.
There is some thought that Vitamin E may be useful, but not universal agreement.
Efficacy of vitamin E in the conservative treatment of Peyronie's disease: legend or reality? A controlled study of 70 cases