I would say "yes," as it's generally good practice to say yes to clever PC ideas. The spell description does make it sound like the spell effect is effectively a big world-ball coated in napalm.
Now, it is big (5 foot diameter!), so I would count it as a Medium creature and simply make it subject to the various relevant Combat Maneuvers - Bull Rush and Reposition being the two most probable candidates (though I could see someone who is fire immune trying to Grapple it to keep it in place). I'd count its CMD as either the caster's CMD using Int instead of Str (remember it's being controlled telekinetically) or maybe their Spellcraft, I'd have to run some numbers. I would rule that anyone doing this would take full damage from the sphere, no save - the Reflex save is you trying to get out of the way, this action would be deliberately forgoing that to make contact with it!
The ball moves with the caster's will and can go up to 30' through the air, so it's unlikely that this will prove much of an impediment (only a giant would be able to bull rush it that far, that it won't just come back on its turn) but it seems like a fun dynamic addition to the battlefield.