Mars is the Lesser Malefic and it can cause small side effects when you first use its energy. You may experience some 'negative' traits and rulerships of mars in the beginning of your workings like intense anger, impatience, increased and/or extreme sexual lust, burns, pains, toothaches, infections...
It depends on how well you can handle the energy and program it to have positive outcomes, but you can sometimes still have small negative side effects. When I first started using Martian energy I started having toothaches and my sexual desire greatly increased and I seemed to get angered and agitated more easily than normal. I also had a huge infectious boil appear on under my armpit but it eventually went away along with the toothaches as I kept progressing further with the mars square and eventually I started seeing positive results. I felt the urge to workout more and I had much more energy during my workouts and I just have the desire to get things done instead of sitting around and being lazy, which was one of my goals for the square.
I also had a small accident where I spilled boiling water on my hand and burned my fingers pretty bad. All of these things started happening at once within the first week of using Martian energy but they eventually stopped and I started seeing positive results.
Scorpio Mars is pretty serious energy and many people can benefit extremely well from it. It just depends on if you can handle the square or using its mantra without being overwhelmed by any negative traits that it may cause to manifest. Keep your AoP up and most of the bad stuff can be avoided.