I had a lumpy rear wheel for a while when a rip in the tire caused a small bulge. I waited three weeks for my LBS to get my special order tires in before I could replace it, but other than being annoying, it didn't cause me any problems or slow me down.

That being said, you're more at risk for flats with lumpy tires. It's up to you whether you get them fixed now or down the road (ba-zing!) when you get a blowout.