You will not have to pay any tax on the capital gain provided that:
(A) the gain is long-term, AND
(B) your total taxable income, including the capital gain, is not more than $41,675 (for 2022, filing as single).
Note that taxable income is not the same as total income or AGI. Taxable income is on Form 1040 line 15. For 2022, if you are filing as single and over 65, your standard deduction will be $14,700. So if your total income, not including the capital gain, is $32,000, your taxable income would be $17,300 plus the capital gain. That means you could have up to $24,375 of long-term capital gain that would not be taxed. (Technically the long-term capital gain is included in your taxable income, but the tax rate that applies to the long-term capital gain is 0%.)
Not all of your Social Security will be taxable, but you have not given enough information to determine how much, if any, would be taxable.
