Hmm, most laptops these days run on 19.5 / 20V I'm surprised it wouldn't be able to handle a 24v input.
If it couldn't it will have burned out the voltage conditioning and charging circuits. If you are lucky they had some series resistors in there as fuses and they simply melted. Replacing them might bring it back to life.
You would need to have some experience in troubleshooting electronics and the proper equipment and spare parts to effect a repair. Not exactly something a website can help you with.
This is an ultrabook by the looks of things, with a 65W charger. If it did burn out at only 4V over, the cost of repair on a base model is close to the cost of a replacement. And if it went out at only 4 over, do you really want it?
If it's under warranty you could try to get it repaired, but Lenovo contracts out repairs to third party companies that rarely hire skilled workers for cost reasons, and are more concerned about churning out units than making sure they actually work.