I've burnt my leg with an exhaust, looks degree2, with a yellowish wound 1.5 inches in diameter&redness around it. Could you suggest proper treatment pls?

Cortisone cream. I agree that there is an increased risk for infection, so make sure you cover yourself for that. Burn need cortisone cream. Over the counter may not be strong enough. I'd see a doctor who can write you a prescription.
Possible infection. Burns of second degree or greater are always at high risk for infections. Since infections need to be confirmed and treated by a physician, best to see your doctor.