Feeling lost not sure what next step is- "I will not promote

​ I'm a software engineer, and on the side, I work at a local game store. I noticed most of these shops don't have a system to manage inventory, orders, or customer data, so I built a web app (web app is mobile friendly but scanner tool to add inventory probably might feel better in an app) and soon a mobile one that works great at my shop. I’m stuck on what to do next. I know there's a market for this, but I don't have a marketing background or a huge budget. Some have suggested partnering with Square or PayPal since I’ve already integrated them, but I don't know how to start. I’d love some advice from people who have been there. I really think this could be a game changer for game stores, but I’m not sure how to scale it.