In my view the word "prick" : to make a very small hole or holes in the surface of something, sometimes in a way that causes pain. It's the best option. Yes, there are other meanings, but it's nobody fault.
"Just a few pricks" It works for me.
A Google search on "Unos cuantos piquetitos" shows that the customary translation into English is "A few small nips."
I don't think this is a good translation because a knife does not "nip." "Nipping" usually means catching something between two points--like a bite. "I got nipped by a dog. I'm fine. It didn't break the skin." "Careful, don't nip yourself with that nail trimmer."
However, "A few small nips" is the usual translation.
Of your two suggestions, "I just stabbed a few times" is better because it sounds more natural. "Wounds" is a somewhat formal word and it suggests the wound itself--the place where the body has been cut open. Also, a "wound" is always serious, while "piquetito" probably means something small and unimportant.
"Stabbing" suggests the action; "wound" the result. A stab makes a wound.
However, "stabbing" has the same problem. A stab is serious. And we can't make it into a diminutive in English, you can't talk about "a stablet" or "a tiny little stab."
I think a good translation might be "Just a few little scratches."
(Here's the problem. The most accurate word I know to describe a small puncture with a knife is "prick," but unfortunately the noun "prick" has a well-known meaning in vulgar slang. I think we can avoid this problem by using the verb form: "But I just pricked her." But, to be safe, it is best to avoid the word completely).
Let me play the role of Sherlock.
Maybe you have not the exact title of the painting, I guess you want to refer to " Unos cuantos piquetitos".
The painting shows us a stabbed woman and the killer with a bloody knife. If this is correct, Frida decided to title the work after the killer's (the husband) cynical excuses in the criminal court : "Sólo fueron unos cuantos piquetitos"
Piquete - Pinchazo -Leve lastimadura con un objeto con punta - A little prick
Espero haberte ayudado.