If you had excess social security withheld you should contact them and let them know of the excess. They should correct it and give you a refund of the excess amount. However, if they do not cooperate you can request a refund yourself by completing IRS Form 843: Claim for Refund and Request for Abatement. Below is a link to an FAQ which will walk you through the process.
https://ttlc.intuit.com/replies/3300261
