Apple leaking a bit of sap

A couple of months ago, I accidentally nicked the trunk of my second year Goldrush Apple, right under the graft union. The wound was no more than about half an inch by half an inch, it was basically just a scrape of the outer bark.

Tree looks fine, but the wounded area, although it appears to be callousing, is wet and appears to be leaking a very small amount of sap. Similar to gunmosis, but not as sticky. Any cause for concern?