How long is he sleeping at night? The older they get the less sleep they need. A two year old needs 12 3/4-13 hours of sleep a day. So if he's getting it at night then he might not need that nap. If that's not the case then maybe a little adjustment to the schedule. My 20 month old son was recently getting up between 7 and 8 and then going down for a nap between 10 and 11 and would sleep for two hours or so and then be up until his 8 p.m. bedtime. That had to be adjusted. Mostly because of our summer schedule, but also because I noticed he was getting very cranky at dinnertime. So now I keep him up until he has lunch and put him down around 12:30 or 1:00. Depending on the morning we've had he usually sleeps until about 3. Some days it might be a little less some days it might be a little more. Depending on how active we were or how well he slept the night before. Sometimes a little adjustment to the schedule is all you need. But it's also very possible he's getting all of his sleep at night. And if you aren't ready for him to give up that nap just yet then you could just make it quiet time in his room. He doesn't have to sleep, but he does have to lay down. You might find that on certain days he might take a little cat nap and that's fine, but other days he might just be up in his crib talking to his toys or perhaps protesting the confinement, but that's find too. If he's getting the recommended amount of sleep a day then he's doing just fine.
P.S. The information on the recommended amount of sleep for children I got from a Parents as Teachers handout. If you'd like to read more about it check out their website at www.parentsasteachers.org.