Sorry if this is a very lay question. I am just an armchair physicist.
The Higgs Boson was just recently discovered, and it has a mass which is considerably larger than a proton. If this Higgs Boson was just recently discovered and the Higgs Boson is EVERYWHERE (ie. The Higgs Field), why wouldn't this perfectly explain the missing mass that is "dark matter" ?
The Higgs Boson can't be a dark matter particle.
The Higgs Boson decays into other particles about $10^{-22}$ seconds after it forms. (So fast that the LHC doesn't directly detect the Higgs, it detects the spray of particles decaying from the Higgs). So while the Higgs field is everywhere, there aren't a lot of Higgs bosons in the universe.
Dark matter must be stable for at least as long as the universe has existed. If Cern or someone else did create a dark matter particle, it would only appear as a suddenly missing mass, since it would be stable, and able to pass out of the LHC without interacting with any of the experiments.
To answer this question, we need to understand what dark matter and a Higgs Boson are.
Higgs Boson
A Higgs Boson is an elementary particle in the standard field of quantum physics. It was theorised by a few people, namely Peter Higgs. The Higgs Field is a field which we can now believe exists, as we can detect it through its excitations, which become Higgs Bosons. The quantum excitations of the Higgs Field create Higgs Bosons.
A Higgs Boson is a particle with no spin, infact, it is the only particle with no spin, electric charge or colour charge. It's also extremely unstable and decays into other particles almost instantly.
Dark matter
Dark matter is a heavily researched topic in physics at the moment. Out of all matter in the universe, dark matter makes up about 80% of it!
One example of a theorised candidate for a dark matter particle is a WIMP. These are abbreviations of 'Weakly Interacting Massive Particles'. These particles are not normal matter, therefor we can't detect them. Our efforts to detect them include trying to look at the annihilation of WIMP particles.
The main characteristics of WIMPS are that they only interact through the weak nuclear force or gravity. They also larger than standard particles (a dark matter particle with mass less than a electronvolt is classified as light dark matter)
Wimps move slowly and are therefor cold, making them one of the main candidates for cold dark matter.
Think of dark matter as a 'skeleton' for normal matter.
Conclusion
From looking at both types of particles, we can clearly tell that Higgs Bosons are completely different from dark matter. We are still trying to find out about them both, as both of them can answer fundamental questions in physics.
