Depends, now that you are retired do you still have earned income to make contributions and the type of IRA that you have.
If you have earned income, then you would be able to contribute up to the contribution limit of the plan or your eligible compensation amount.
After tax contributions can be made to a traditional IRA or Roth IRA.
Some 401(k) plans allow after tax dollars contributions. You would need to contact the plan administrator to check if that is allowable.
