Thanks all for putting my mind to rest.
I was worried that because the bike was in gear, I may have stressed something internal to the autolube pump.
Heading off for my first outing very shortly...
 

If you are not at 100% at rest , not trying to yank your chain here, take it off and look at the gear inside.
They're fragile, i know, i've snapped one and you will hear it and it's not hard to snap. The scroll it goes on to is much harder.
It's two screws and a fresh gasket and 10 mins bleeding the pump. If anythings broke trust me it will fall out.
I don't think it works like that anyway . There's two ramps ,plungers and springs inside on the inner side of the gear . When you turn in that direction it pushes the plungers in and the shaft turns not the gear.

I read the other guys have put your mind at rest but my input is the plastic wheel only has a very small cotter pin going through it, and surely that would break if any resistance happened.
On another note, nice idea with the nail, I was personally thinking I'd get an old pinion drive out of my sons RC collection and run it in a drill to the side of the cog.