If the check is made out to a financial institution for your benefit, it's not payable to you personally so there should be no need for you to endorse the check. As Opus 17 said, such a check can only be forwarded to the financial institution for deposit into the receiving retirement account.
If the check is made out to you and you do not roll the funds over to another retirement account, you will be taxed on the taxable amount shown in box 2a and, if you are under age 59½, you'll also have a 10% penalty.
