Put it on dumm (simmering ring) again - low and slow is the best way. You can also cover it with foil and put it in the cold oven, turn oven to 170c, once it is at 170c let it heat for 5-15 mins depending on quantity. Another way for future is not to add the rice until just before the guests are coming, cook the rice at the last minute.
Put it in a foil tray, cover with foil, and pop it in the oven for about 35-40 minutes on about 350-375 on the middle or upper rack
I do it by popping it on the stove and adding some water to keep the moisture in. Like a few dabs of it. And to stop it from burning, I put a flat pan which you make chapatti on aka a tawa