You are only allowed 1 dispute per transaction so the only way you can get a second dispute opened is to contact Paypal (when and if you can) and see if they will open a second dispute for you. They may decline citing policies but if you say you made a mistake then they might open a second dispute for you....but unlikely if you closed it yourself.
If not then if you funded your paypal payment via a credit card then consider contacting your card issuer and see if they will help you with a chargeback?
Advice is voluntary. Kudos / Solution appreciated.