groin/hip flexor pull!

Hello! My name’s Nicole and I’m currently training for my second half marathon, the NYC Half this March. I recently however, took the week off due to a pretty painful groin pull that has been creeping up on me over the past few months. It seems that whenever I increase speed while running, my right hip, close to the inside of my thigh, becomes pretty fatigued and painful. I got a massage this week which relieved some lower back pain, but the hip flexor pain is continuing. At this point I’ve been resting as much as possible but would love to get back to training. Any insight would be extremely helpful!