Nope not wrong

Well the celtic cross isn’t a viking symbol Bert! 😉 It’s Irish and christian.
The celtic cross as you know it today was mainly used for decorative purposes on graves, but a lot of the newer imagery has a neo nazi origin, so I’d tread carefully if I were you. But it really has very low religious meaning or any other, it’s mainly just.. Pretty. It’s been popularized to death. The knots themselves originate from the old Roman empire, so I honestly doubt you’ll offend anyone (well unless someone mistakes you for a neo nazi), except the future you.