You can reimburse yourself with a distribution from your HSA at any time in the future for medical expenses incurred after the establishment of your HSA and were originally paid out of pocket. As others have said, since you already have a HSA account, pay the medical expense out of pocket and at some later date when there are sufficient funds in the HSA, take a distribution from the HSA to reimburse yourself for those expenses. Just be sure to retain receipts for the medical expenses in case the IRS questions that your HSA distributions were actually used for qualified medical expenses.
