How can i prevent dry eyes from incomplete closure of my ptosis when i sleep? is it okay if i tape it or use an eye mask at night?

Use : Eye lubricant ointment at night to keep your eyes from drying out!

Depends: On how bad the problem is. You could start with using an ointment, like refresh pm or lacrilube, (artificial tears) at bedtime. If this is not sufficient, you can use a night-time soft goggle to hold the eye shut. Of course, you could see an oculoplastic surgeon and get it fixed as well.