Spreading Red Welt Rash, What Is This Rash? Is It Poison Oak ? Please Give Me Your Suggestion For Treatment

About 10 days ago, I came in contact with some poison oak. There's some contact dermatitis on my arm and neck. Three days ago, I discovered a lump in my groin. I assume it's an inflamed lymph node, as it's small and painful to the touch. In the last two days, an itchy, red welt has appeared on my upper thigh. It started small (when I first noticed it, it was about 3 cm diameter), but has now spread to the size of the palm of my hand, and another patch has developed in the joint of my leg (same area as the inflamed lymph gland). There are some petechiae in the reddest part of the welt, which I assume is from my undisciplined scratching. I've been treating the poison oak with triamcinolone acetonide cream and benadryl. When the welt first showed up, I applied the triamcinolone to it as well. I've stopped, as I'm wondering if it might be unrelated to the poison oak. What is this rash? and what can I do to treat it, and keep it from spreading further? Here are some images - 1. - Leg and groin rash - http://i94.photobucket.com/albums/l114/ltalathiahiggins/IMG_9950.jpg 2. - Poison oak rash on arm http://i94.photobucket.com/albums/l114/ltalathiahiggins/IMG_9954.jpg