increasing back and leg pain

hi

for the past few weeks i noticed a lump on my lower back which has not grown in size, i was so afraid of having cancer that i went to the doctor and he felt the lump and told me it was a natural lump of the back. the lump is about the size of a grape and from the day i found it i was experiencing lower back, groin and right leg discomfort. (no actual pain). the doctor put the pain down to anxiety and after the visit i am glad to say that i have beaten the anxiety, i confirmed this because i am thinking much more rationally about my symptoms and my sleep patterns have returned to normal and the feeling of general malaise has gone too. my appetite has returned also. however within an hour after i get up out of bed i begin to feel mild pain in my right buttocks and leg, the pain doesnt shoot down but its there. sometimes the pain seems to be coming from this lump on my back.. with the absence of any neurological symptoms i am willing to accept that i do not have a serious condition, although possible, very unlikely. i was wondering, should i get a 2nd opinion .. the doctor was rather dismissive however he seemed quite positive that the lump is a natural muscle or bone that comes out from the spine, i asked if he was sure 3 times and he assured me its nothing to warrant anything. however i am concerned because my anxiety seems to be gone yet the mild constant pain persists.. any advice??