How to locate cities/addresses near from a specific address

Hello everbody !

I am making a website in which I would like to use openStreeMap. I have found https://wiki.openstreetmap.org/wiki/Nominatim to search for addresses and locate them on map, but I would like to locate points near a specific address. I explain : I will have persons registered with their addresses, and anyone can search for people around his position, for example 30km from where he is. As all the addresses will be in a database, I thought I could search for cities near the address, and then search for these cities on my database.

So my question is : do you know how to find cities around a specific addresses ? Or maybe (an idea that comes now) there is something to do with coordinates ??

Thanks for you help !

Jonathan