would be a good thing to do if there is doubt.
I would check for swollen joints near the problem area.. it may be a sign of MBD (metabolic bone diesase). If that's the case, he will need treatment and UVB/Sun to help reverse the damaged effects.
Check for bites... crix can nibble/chew on dragons and cause sores or wounds.
Sleeping on the bottom of the cage is normal. If the dragon cannot walk on it's foot, that is not normal. It's possible he hurt it while jumping or falling off something.. in which case a vet would be good to examine the dragon.
Hope he's doing better for you soon.
brandon
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Dragons by Nature