You may have blown the main fuse for the starter relay. Easy to do. If you follow the red positive battery cable to the starter relay (most models) you'll find the starter relay at the other end. There should be a fuse in the relay or in a panel on the atv. Same type square standard sized boxed fuses car use. Best place to start. If you comment or answer with your year, make, model and engine size I can provide a better answer.
All The Best, Justin McCartney
17 South Industries, LLC
**FYI - that's a pretty standard starter relay. That's for a Yamaha Bear Tracker - two fuses - one is the main and the other is a spare that you can pull out and use. When the fuse blows no power. - With your lights - they will still work if attached directly to battery. Relay won't if fuse is blown.
29, 30 & 31 are the starter relay for the model this diagram goes to. Usually the relay is going to be close to the battery, by the way.