If you really haven ridden it much then I would def take it back and have them take care of it for you. That shouldn’t happen on a new bike that was hardly rode. Also like what JG said above, that’s the major advantage from buying from a brick and mortar store.
With that said, it could be something as simple as having some dirt built up in your seat post, bottom bracket and/or your pedals. I’ve had every one of these situations happen and sometimes they can be difficult to diagnose so I just tear it all down to clean and grease it all and it goes back to normal!