As you can see, the cut is almost an inch long, so not really small. It's impossible to wear this blouse without fixing the cut.
After sulking for half a year and pondering about how to fix this, I opted for cutting right throught the sleeve and insert a lace strip. I chose between three options: the first is a simple cotton strip.
It was ok, but really white as opposed to the slight off-white of the blouse. Hmmm, not sure.
The next one is a small lace strip that I really like, but it's quite stiff and I'm afraid it will scratch my arms every time I move. A definite no, this one.
The last one is a broader lace strip, and a lot softer than the second one. The colour is also exactly right.
No going back now...
And because I could not do only the left sleeve, because that would be really silly, here is a picture of the blouse with both sleeves altered.
And since I had some leftover lace, I decided to alter the bow bit.
And so, one year after purchasing it, I'll finaly be able to wear this slightly altered blouse to work.