Not sure if you're back to 100%, but I suggest reading the other threads here and on Lets Run and Runners World about Extensor Tendonitis.
I've dealt with this injury twice now -- both times as a result of training through a marathon and it came up in the training runs the days after the marathon. So in both cases it was simple overuse for me (I'd been running intense miles the first time around, and lots of miles the second time around. So here's a recap of my experience/solution:
1. Rest: The most important factor is to rest it until the pain is gone, and then gradually start adding mileage until you're back in your groove. You could use an Air Cast to make it easier to walk and largely immobilize the foot.
2. Reduce Inflammation: From what I've read and experience, the Penetrex cream was helpful (and it's safe not to use DMSO), and regular ibuprofen, icing, and epsom salt bath/soaks. Before I resumed any serious running, my strategy was a daily combo of all the above tactics, combined with the rest until I was pain free while testing walking, jogging and going up/down stairs (including for a day or two after that testing). These are two good cold wraps ((Option 1)[http://www.amazon.com/Elasto-Cold-Wrap-foot-Ankle/dp/B0017LB4ZG/] & Option 2) for this part of the foot (I preferred the second one). The second one doesn't do double duty (no heat option), but I found it was the most effective of the two.
3. Circulation: Once the inflammation subsides, a hot wrap or other therapy helped to increase blood flow to promote healing (ordinarily. there's not much blood). An electric wrap like this, or alternative one you heat up in the microwave was also helpful. Once I had no pain, I also did a lot of stretching to help.
4. Start Back SLOW (w/KT Tape): You can tape it when you resume running to help prevent recurrence, as in this video. The second time I got this injury, I caught it early enough, that I was still able to run a mile+ each day to keep a pulse on how the healing was progressing (but it was a pretty light jog, so as not to make it worse).
5. Stretch: In addition to the tight laces or the wrong shoes for your form, overly tight calves, feet and toes can all contribute to this injury. Additionally, other form issues, such as tight hips, ITB or knee issues can cause you to overload the foot and inflame these tendons. So once you get over the injury and start healing, be sure to address the underlying form or overuse/training issues that cause the injury in the first place -- otherwise, it simply appears to return in a lot of runners.
I've read all kinds of varying advice on this from ('run through it')[http://running.competitor.com/2014/03/injury-prevention/injuries-that-arent-injuries_72338/3], to some pretty (detailed strategies)[http://davidstrialofmiles.blogspot.com/2012/06/injury-update-extensor-tendonitis.html], and (some real sagas)[http://community.runnersworld.com/topic/foot-extensor-tendonitis-resume-running]. From what I read, this is something that some people linger with for months or almost a year+ when they never let it fully heal before resuming running. So I would be sure to assess yourself based on how you feel and be careful when getting back to running.