I had my Lasik 3 weeks ago and I accidentally hit my face with a cord and my left eye got watery. Should I worry?

The most important question is how is your vision in your eyes? If it is good then you probably did not cause serious damage. If however your vision is poor or worse then you need to see your surgeon asap. If the vision is good, tearing is improving and you don't have any pain or thick yellow or green discharge then you may be ok to watch it for two days to see if it resolves on it's own. If otherwise then you need to call and see your surgeon.

You are probably fine, especially if your vision hasn't changed. If there is any doubt, or if you have persistent watering, eye redness, eye pain or vision changed you should be checked immediately.