We have a sweet cherry tree that developed a canker on the trunk and it wept sap everywhere - I thought for sure it was dead. I cut the canker out and sterilized it and the branch right by it still doesn't look damaged. The sap gets really hard. That looks like not enough of the sapwood got really deeply damaged.

Keep checking around the base of the tree, though. Ours keep getting borers and your first hint is something that looks like gobs of jelly around the base of the tree. Ours took a really hard hit this spring and have looked sickly all year. Yours actually looks much more healthy than ours and we still got peaches off ours. Our whole trees are having the struggle with the curling leaves because so much of the sapwood got damaged by the borers. This year we're putting milky spore into the soil to see if we can make sure there won't be those durn little grubs chewing into the base of the tree next spring.