Log into your digital keys software account (if you are account administrator) via another phone, and access your account, and hit the remote unlock button in the software. If you are not an account administrator, please call them (and they could help you enter by hitting the remote unlock button in the software.
Also please take whatever measures you did in the past with your metal keys to avoid a lock-out. All of our commercial NB IoT smart locks come with metal key over-rides for emergencies. Did you give a spare copy of the key to neighbours/friends/family, do you have a spare metal key in your wallet, handbag? You could also carry a spare NFC token in your wallet, on your phone as a NFC sticker etc. If all back-up plans fail, you may choose the services of a professional locksmith to give you access.