Um... if this is FO2, I know you can hold right click and choose the hand and arrow option, then your ally will move. Though this may not work in your current situation.
This.
Except if you're refering to Fallout 1 Dogmeat, then there is no 'push' command, NPCs are my weak point, but I
'assume' Dogmeat will amble out of your way if you're patient enough, if he hasn't after a minute, I'd say you'll have to reload.
It's frustrating I know, but it was something that was addressed in Fallout 2, so it clearly was a big problem in Fallout 1.