As others have noted, the total energy equivalent is that of a moderately-fast baseball throw, which, in the case of a baseball is perceptible but generally not harmful.
The transmission mechanism for the baseball is the electromagnetic force, where the individual molecules of the baseball are interacting with the individual molecules of your body, and the imposed and reactive forces are roughly equivalent.
In the case of the OMG particle, as a proton it would exert a positive charge, and might steal an electron (becoming a hydrogen atom in the process), or interact directly with a nucleus, though likely splitting that. The atoms of your body are principally carbon, hydrogen, oxygen, and nitrogen, atomic numbers 1, 12, 14, and 16, respectively. The result of such an interaction might be isotopes of: H, He, Li, Be, or B, numbers 1--5 inclusive. There would likely be a chain of such interactions depending on the effective cross-section of the incident particle, atoms in your body, and any collision particles, though this is pretty much where my physics knowledge abandons me.
Online sources suggest that this is pretty accurate: the particle would pass straight through you:
<https://www.technology.org/how-and-why/if-proton-nearly-at-l...>
Presuming there is a collision within your body, at this point you have a particle stream, interacting with other material through electromagnetic and nuclear (strong and weak) forces. Again, you're dealing with exceedingly high energies, and it seems likely to me that those particles would tend to exit your body and have further interactions with the surrounding region (air and solid matter), which would result in some local ionisation and light heating. The question is the interaction cross-section of the incident particle, atoms within your body, and any collision and decay products.
Point being that you don't want to necessarily direct the maximum energy at a target, but the energy that will disrupt or interact with that target in the manner in which you intend.
Cosmic rays are striking your body all the time, though at lower energies. The effects tend to be local ionisation and, most critically, damage to genetic material. The latter is the most significant from a biological perspective.