When the fish gets bound up like that, they become lethargic.. get real inactive. Like we do when we don't feel good. As the belly gets full and the fish can't poop, it usually sinks down toward the bottom of the tank. That extra bulk displaces the air space inside which degrades it's natural boyancy... so watch for behaviour changes like that, hovering at the bottom or struggling to swim upward only to sink down again fast (even rollling or flipping upsidedown), leaning off to one side or the other, an inability to swim in a straight line, and no eating or pooping.
Whether it's hungry or not, the fish won't be able to eat much more than what's still inside. That's okay for several days so it doesn't get further impacted. Don't even try to feed it for 2-3 days or so (judge that based on how young it might be). Then try to feed it the inside part of a few peas, mushed up. (Use only fresh or frozen peas; not canned.) The fish will be hungry enough to gobble that up despite the discomfort. That provides enough fiber to loosen up the blockage. From there, make sure the fish get more vegetable content than protein in their diet.