Unfortunately, like claymore-wielding warrior-women, this is one of those ideas much-beloved of some of the "D&D school of re-enactment", although it's usually Vikings rather than anglo-saxons.

This isn't to say that it's wrong, just that I'm not aware of any source in the period that mentions it, or any actual evidence other than the following;

We DO have classical references to Saxon tattoos (....from at latest the fifth century, so about as valid for immediate pre-conquest as reconstructing a vietnam marine using evidence from shakespeare)

We DO have evidence that the Saxons knew what tattooing was, but not that it was either generally widely used, or in any way "ritual" in nature (....so maybe roughly like the 1950s position - some people have 'em, most don't, nobody thinks they're anything but body art)

We DO have tattoos on a couple of the bog bodies excavated in the c19th, but none from the UK or from the immediate pre-conquest period. Again, however, far more don't. As to whether those that do are "ritual"..., well, who can tell, as the bodies are completely contextless?

However, I don't claim to be an anglo-saxon specialist, and could be whoever mentioned it to you has sources I'm not aware of. I'd definitely ask them before I accepted it, though.