Don't think of "falling in". Instead, think of "moving in a straight line". I assume you've learned Newton's la of inertia, so it's clear and intuitive to you that if a puck moves on a frictionless horizontal plane it will just carry on moving on a straight line at constant velocity.
Now to think of GR, people tell you to think about a curved surface, rather than a plane. But the important thing to realise is that this is just an analogy. The real "curvature" isn't like that, but is abstract.
What you should do, is imagine this situation from above. In the Newtonian case, the puck just continues in a straight line. In the GR case, the puck appears to move in "non-straight" line. Ignore the fact that in the GR the surface is "curved" - it isn't really bulging in real-space, that's just an analogy to make the trajectory from above look curved. The point of it is that now the puck moves in a "line" that appears curved to us. No forces are acting, the puck is still moving inertially along the line of inertial movement.
One way to say it is to treat the inertial-movement line as the definition of a straight line. So you keep the Newtonian idea that inertial bodies move along a "straight line", only now this line appears curved in 3d-space. This is like how a circumfrance-line of a sphere is a "straight line" along it, i.e. it's the shortest way to connect two points along it, even though the line is actually curved in 3d-space.