Damaged Mop Top Trunk

Hi there, yesterday I discovered that someone (!) mowed my lawn but knicked the bottom of my Mop Top Robinia with the mower. Needless to say I'm worried that this will either sucker, or get infected (as I've read they sucker really badly & I certainly don't want this!). The cut is about 2in - 3in in length but only quite shallow, might go in 1cm or so (more like a slice down the trunk).

Does anyone have any suggestions as to how I should best repair this to minimise the chance of suckering? The tree is only young, although about 8ft tall, still has a thin trunk, about 3cm's in diameter. The damage is very close to the ground, about 10cm's up the trunk.

I'm planning on strapping up the slice to the trunk with a bit of stocking or zip-tie. Would anyone recommend treating wound first? Advice would be great - Thanks!