I have had several patients with this problem. Patients get false lashes, then trim the lashes and end up trimming their natural lashes too. Most often I recommend Latisse. Latisse is a medication used to lengthen, darken, and thicken the natural lashes. It is applied with a tiny brush on the lash line at night. Optimal results take about 16 weeks, but you'll start to see results at about 30-45 days. Give it a try!
If you mean you cut your lashes (as in trimmed them), you don't need to do anything as they will grow back. It would be wise to avoid everything and anything. It's the same as it you don't like a haircut- with time if grows back. If you meant that you injured the skin that the eyelashes grow out from - you may wish to see a physician right away.