Since we don't know whether you took the standard deduction or itemized deductions on your original return it's not possible to answer your question. Add the deduction to your tax return and see what happens to your refund. If it increases then it would be worthwhile to amend your return to add it. You must delete the amount you add after you have seen what it does to your refund. Even if you decide to amend your return, the return as you originally filed it must be used to start your amended return form 1040X.
Here are instructions for amending a return: https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed
