How Can Toe Swelling With Pain Be Treated?

Hi, my son was out at our county's Relay for Life even this weekend. His socks and shoes got wet and he wore them for a while like that. Now the side of his toe is red and swollen just a little. He says it hurts to walk or even touch it. From everything I've read is sounds like a very mild case of trench foot. How do I treat it? He is 10 years old, about 4ft 8 inches, 100lbs - medical history of asthma and frequent upper respiratory infections, other than that, he's been very healthy.