Does anyone know what this could be?!! I woke up little over a week ago with my foot swollen and a red spot. I never…

Does anyone know what this could be?!! I woke up little over a week ago with my foot swollen and a red spot. I never injured my foot & There was absolutely no type of hole, so it’s not a bite. It hurts to walk and is causing a ache in my leg similar to growing pain. I went to the ER a week after as it still hadn’t gone away, only gotten worse. She numbed the spot and made an incision (as seen in pictures) to see if it was infected/any puss. There wasn’t. They sent me for an ultrasound on my entire leg to rule out DVT (a blood clot) it came back negative but they never gave me an answer on what it could be or what to do. I also asked my Obgyn before the ER and he made me feel stupid for asking for his opinion. He wasn’t worried about it at all, and said to just been seen by a regular doctor. The ER told me to follow up with my OB if no improvement, but obviously he doesn’t know.. I’m 29 Weeks pregnant so it’s causing lots of stress that it could be something serious. Please any advise it appreciated!