Hi @Jemz92 is your skin red and itchy but in tact or has it broken down and is peeling?
If in tact the solugel should be fine but I'd recommend keeping it in the fridge as it will be nice and cool to pop on. Also it may sound strange but the old wives tales for mastitis of cabbage leaves works wonders (keep in crisper then place over your skin but only if your skin is in tact)
If your skin has started to break down I would recommend visiting your radiation nurses (you can go back to them even though your finished) and get some dressings . Mepilex lite dressings are great (like a thin foam) and also they should be able to give you some gel pads for your nipple.
The skin reaction tends to peak about s week after finishing but should ease about 3 wks after. Xx