Hello, I Have A Almost 3 Year Old Son Who

Hello, I have a almost 3 year old son who is going through potty training. Today I took off his "in case of accident while napping" diaper and there was a string of mucus with a little blood in it. Should I be worried? Is this something that needs medical attention? He has had no change in diet and nothing else is out of ordinary. Thank you so much for your time.
Sincerely,
Tiffany Kurth