What's up with my plum tree?

I was checking out the fruit trees today and noticed a sore/wound on my 1 year old plum saplings.  I planted them bare root last spring.  They grew well but the deer tore through our wimpy fence and tore off branches and ate the ends off.  This spring they started growing well again.  They main leader was bent so I used the driveway marker stake to train them.  I noticed two bumps on the old wood of the main stem and got a few photos of it.  Can anyone ID the issue from these pictures?  Thanks!!!

I don't know if it's my vision or the picture but I can't get a great look at it.  Plums are particularly susceptible to black knot.  Black knot can take hold in any bark crack or other tree I njury.  Give it a quick google.  
You might be at the beginning stages of it here but like I said I can't quite make out the picture on my phone.  Early stage black knot is typically hard to identify.  I would be curious to hear what everyone else thinks.  
If your tree has black knot you will be able to identify it better in the dormant period as it stands off a lot more.  
Once winter hits you want to prunye off the infected area.  It's a fungus and can spread so be sure to prune at least a few inches 4-6" on either side of the gall.  
After pruning clean your equipment throughly, gloves, clothing and pruners so you don't spread it to any of your other trees.  Lastly dispose of the infected wood.  

Thanks Dave, I looked up black knot and it looks kind of like the same black stuff that grows on cherry trees around here.  This seems more like a hole or old broken off twig that is getting grown around in a funny way.  I zoomed in on the two bad spots, maybe this will help with identification.  Or maybe it's early stage black knot...  FYI there is a black ant in the first picture.