Tire leak on rim

I've had my G2 for 2 months and I found out the rim was leaking air. I tried tightening the screws, but they were already tight and one screw got its head broken off. I was one of those guys that bought it for 700 dollars on Walmart, so I'll let you guys know if warranty covered it.

If ninebot doesn't send me a new tire, is my next best bet injecting sealant in the wheel?