to hit someone or something by accident while you are driving
Example: A truck ran into me (=hit my car) at the lights this morning.
to reach a particular amount
Example: Flood damages could run into millions.
to start to have trouble/difficulty/problems etc
Example: For some part of her, a part she'd lost touch with, wanted to run into his arms.
we run into each other somewhere.
So yeah, we're in the scene as we are rolling down the hill after Merry and Pippin run into us, running away from Farmer Maggot's Field, having stolen a bunch of vegetables.