I noticed my hose is rubbing on the PS pump too when I took my headlight out, but it's still good for the time being. It's a pain to replace because I watched my friend do it on another Focus; and it's all molded into one piece.
You'll either need some long pliers or the special hose clamp pliers with the cable that lets you get into tight places.
Dunno how you guys work but I can swap that hose out in a minute or less with a simple pliers.
You can't just replace the small hose if it's the factory hose ... if it's an aftermarket hose, say Gates:
Then you might be able to. But there is no replacement part # for the small hose only, you'll have to Jerry-rig something.
So, replace the whole hose.
Some advise for anyone who might have that hose rubbing anything ... you should be able to rotate the water pump end and/or the radiator end to give more clearance to whatever is in the way. If that does not give enough room you may need to trim one end of the hose just a bit, but be aware that the radiator side is expanded some. So don't trim too much or it'll be very tough to push on.