I really need help

My son started to walk few steps and I noticed that the he has diaper rash and redness on his private parts and also his thighs. I thought maybe it because of the fraction when he is walking. I really don't know what to do

I change the diaper brand

I use desitin maximum strength for the rash. It worked but he started walking more and it came back!

I'm really lost I don't know what to do. We clean him with water we don't use wipes.

We let him butt nakes for 10 min each change. I really don't know what to do.