Definitely put a patch over the hole, inside the tire. What can (and will, on semi tires) happen is, as the tire flexes, the cut will keep "nibbling" on the tube until it worries a hole in it.
We used a patch that looked like a giant thumb tack. Prepare the inside of the tire with solvent, then glue. Fish the "sharp point" end of the "thumb tack" thru the hole, from the inside, then pull it thru until the underside of the thumbtack connects with the inner layer of the tire. Pull it tight, then roll the patch down from the inside. Snip off the excess stem, talc the glue area so it doesn't stick to the new tube, and your ready to install the tube.
Its going to be hard to source that ^^kind of patch, but a regular patch that's used on tubes will suffice. If the tire is a radial, you need to find a patch rated for radial.
Edit: in retrospect, if you have to take the tire off the rim anyway, just patch the tire from the inside with a appropriate patch onto the inner liner. Prep with solvent, grind or buff the area until smooth, apply glue, let dry, then apply patch and roll down. Might be easier and just as economical to have a tire shop do it.
I've done my own tires all my life, as well as hundreds or even thousands of car, truck, trailer and wagon tires, and this is how i do it.
