As long as you didn't include a Traditional IRA Deduction on your return, checking the sick pay box instead of the retirement plan box didn't have any affect on your return.
However, if you did include a Traditional IRA Deduction on you return, you may need to Amend your return depending on your income. I suggest walking through Amendment process in this case to make sure checking the Retirement Box doesn't affect your ability to take an IRA deduction.
You can click here for instructions on Amending your
tax return: How
to Change a Tax Return You Already Filed.