What Causes Groin Pain Along With Difficulty Walking?

Hi, I have had groin pain for about 4 weeks now. At first I couldn t put any weight on my left leg/groin but after rest, I can now. I have noticed that my walking strides are shorter, sudden/sharp movements and carrying heavy objects cause me alot of pain. My groin does ache in the evenings an I still find I cant do any running yet. I have been doing exercises to help stretch it, an build it bk up. But I have noticed now that the pain is now going from my groin to knee?? Any advice would be great full x