NHS and tattoosWatch
It's not offensive, but it could be deemed a religious symbol which is probably somehow offensive to someone who is a little sensitive. The NHS may interpret it negatively as it's not easily hidden, so I'd ask yourself if a tattoo is more important than the career you want.
http://www.southernhealth.nhs.uk/_re...ll/0/44077.pdf (section 6.5.2 in this file)
While I do know of many doctors who has tattoos, they are usually out of the way or concealed. So, as @hannxm says it's tattoo or (potentially) career)