How old is the liner?
If the liner is in otherwise good shape, a patch should be fine. Liners as they age get weaker and weaker. So if this cut was due to something specific, go for it. If a mysterious reason, and the liner is old, you may get more in other places starting to show up soon - then replace the liner. The life span of patches varies a lot, but I have gotten several years out of some. Enough to stretch things to the point where I really did need to replace the whole liner. But if the patch starts to leak sooner than expected, it is really hard to patch a patch - so then new liner time.