Expired F1 visa [closed]

You cannot re-enter the US without a valid visa (there is an exception for Mexico and Canada). You can however use the I-20 to get a new visa issued from the consulate. It is better to do it from your home country, but you can consider trying from Estonia as well if you can give them an acceptable reason for why you are doing so.

You should consult your university's international students' office for better advice on where to apply and when.