The following is taken from a pelvic surgical atlas. Most Ob/Gyn's have experience with these issues and have seen it many times as a result of birth trauma.
Hematoma - vulvaAs noted in the discussion of pelvic anatomy, the superficial compartment of the anterior perineal triangle communicates with the subfascial space of the lower abdomen below the inguinal ligament. Little tissue is available to tamponade bleeding into this space, even from the low-pressure venous system; thus, a hematoma can extend from the posterior margin of the anterior triangle (at the level of the transverse perineal muscle), anteriorly over the mons to the fusion of fascia at the inguinal ligament.
A hematoma resulting from venous bleeding, although it can form rapidly, stabilizes at the above margins because of the low-pressure nature of the bleeding and may be managed expectantly. On the other hand, a rapidly expanding hematoma that does not stabilize is more likely to be the result of arterial bleeding. In such an instance, an incision medial to the labium majus permits evacuation of the hematoma. If possible, identify and ligate the source of bleeding.
From your brief history and photo, the bleeding sounds stable and was venous in nature. I will caution against surgery. However, you need to be examined and have the suture line inspected immediately.