Could The Knee Injury Be Infected?

i fell off my bike about a week ago. and although it was a big scrape, it didn't bleed at all. once i got home 2hrs later i cleaned it with alcohol and washed it. i've been putting clean gauze every day and bandaging it whenever i hit the trails. it's already scabbed up. but you can see a red outline around it. it's not hot, but i'm worried it might be infected. it hurts more when i poke the actual scab than the surrounding. a foot below, at my ankle, i scrapped up a bit, and it's now a bit swollen, if the top wound is infected, could the infection have run down to my ankle? that one doesn't hurt when i poke it, and the scab is already falling off.