When a foreign body enters your eye, be it dust, a lash, anything at all, extra tears are produced in order to eliminate it. This is a defense mechanism to help expel the foreign object from the eye. The tearing usually stops when this has been achieved. The eye would also respond to the foreign body by being red. It’s best not to rub your eye when something has gone into it, because you might just embed. The best response is to rinse the eye with clean water. If the foreign body was something sharp, or dirty, consult a healthcare professional to further assessment. Antibiotic ointment or drops may be necessary to prevent an infection, if the cornea is involved, a bandage contact lens can help with healing.
In some cases, you can develop a cyst in the eye, which will feel like a foreign body, the easiest way to distinguish between the two is that a foreign body will move around as you move your eye and blink, a cyst will stay in the same place, consult an optometrist for assessment in both cases.