Hugs hun
When you let him sleep for his nap did you also push his bedtime later? I think there are lots of LOs who go down to 10.5hrs night sleep before they drop their nap. So if it is just that he only needs 10.5hrs at night for the time being you would have 2 options if cutting nap doesnt work a) Keep 2hr nap, push bedtime a bit later b) Let him sleep for nap, and also push bedtime later.
Does he have his molars or canines yet? Those teeth were the absolute WORST for dd1. She never woke early until she started teething her 1yr molars and canines. No matter when or if I medicated they still caused ews...12months to 18months was the worst age for dd1 sleep wise
If it isnt a schedule issue, then it is probably those teeth, and there may not be anything you can do about it
When he wakes at 5/5:30am is he happy? He could be hungry, Im sure he wouldnt be the first LO to ew during a growth spurt!