Depending on the misspelling you may be fine. The IRS will verify the beginning letters of your last name and your Social Security number with what your Social Security Card is showing. If you have already filed your tax return you would need to wait and see if the return is accepted or rejected.
If rejected, you can go back and correct the spelling then re-submit your tax return. If accepted, you would not need to do anything any further, just be sure the spelling is correct on next year's tax return. This will have no effect on your tax refund and will not delay it any way.