Hmm - I think I know what yer talkin' about, it's a lil odd as most have the opposite prob, thus the confusion.
Look under/in the pin lock mechanism, you may have a bit of casting flash blocking the recess where the pin seats while in the locked position. If so - that's easy enough to clean up. If not, I suppose you could reshape the lil cove where the pin seats to lock it or simply bend the lever a bit so it doesn't hit yer grip - but I'd be hesitant to do either of these as mostly the lock doesn't work well enough to prevent the clutch from dragging for many of us and you may find as your clutch wears in - it could end up being perfect *shrug*.
By far the simplest way to deal with this is a 1 1/2" - 2" section of old inner tube on yer grip, using this as a "rubber band" to hold yer clutch in while pedaling distances or idling for prolonged periods and this is far safer than trusting that locking pin - should you inadvertently hit that lever while tinkering, your bike could launch w/o you o.O
It's interesting tho - the first lever I had, the lockout was useless and the clutch would drag. My buddy stuffed up my bike and as a result I got another clutch lever and tho it looked absolutely identical - the lockout worked great o_O
I still prefer to use the inner tube trick