"Si esta víbora te pica, no hay remedio en la botica" is a Spanish saying which is literally translated: "If this snake bites you, there is no remedy in the pharmacy". Surely you've seen written on a knife of Albacete (Spain), where is very common to incise sayings on the leaves of the blades. So, it means the danger of that knife.

It means that if something happend to you, nothing can be done to solve it. For example: "If you meet that woman you´ll fall in love with her". The example of the knife of Albacete is very good too.

I see. I've also heard it translated to the English expression: "You're playing with fire." Is that a fair translation?