Important Stelara question

Hi. Had my last Stelar injection at the beginning of July this year and tomorrow I'm due to start a course of light treatment. (came off Stelara because of crappy side effects) The specialist light Derm thinks the Stelara should be well out of my system by now and therefore should be safe enough to start lights. (though he really wasn't certain and only decided that it was probably safe after a quick search on Google) But I'm still feeling some of the side effects from the Stelara. Plus the fact that my skin is deteriorating a LOT slower than it normally would, it leads me to believe that the Stelara is still in the system and starting a course of Puva light treatment now, could well be an unnecessary skin cancer risk? If anyone has some sound concrete advice on this it would very much be appreciated. Thanks for reading. Cheers