Mild Sunburn. Advice?

Ok so I tanned in a tanning bed today for 20mins and now I have these odd sunburns all over my back side. I tan very easily and the sun burns don't hurt. Are they just mild and will go away tomorrow or will it take a few days? I have a banquet to go to tomorrow night and I am wearing a short tail dress so I dont want to look horrible!! And if it will take a while for the burn to go away any advice for covering it up?