Will crying a few hours after treatment ruin under eye fillers?

I would not expect crying a few hours after under eye fillers to influence the ultimate results of the filler. From your description, I doubt that you cause any harm.  

Assuming the fillers were injected properly, it is extremely unlikely that crying after your treatment would cause any migration or problem with your fillers. That being said, should you have any further questions or concerns, there is no substitute for a follow-up visit with your provider to go over your results.