As far as I know, a principle is a collection of facts bundled into a general statement - these are easier to learn from in my experience.
But what would a concept be as opposed to that? A philisophical mindset put into a statement?
According to what you find in the dictionary, principles are more concrete established facts and truths.
1. A basic truth, law, or assumption: the principles of democracy.
a. A rule or standard, especially of good behavior: a man of principle.
b. The collectivity of moral or ethical standards or judgments: a decision based on principle rather than expediency.
3. A fixed or predetermined policy or mode of action.
4. A basic or essential quality or element determining intrinsic nature or characteristic behavior: the principle of self-preservation.
5. A rule or law concerning the functioning of natural phenomena or mechanical processes: the principle of jet propulsion.
Where concepts are more general and less well defined.
1. A general idea derived or inferred from specific instances or occurrences.
2. Something formed in the mind; a thought or notion. See Synonyms at idea.
3. A scheme; a plan:
In terms of martial arts, I liken principles to physical, tangible things, like the proper structure, good mechanics, alignment, etc. While concepts are more like mental strategies. But that's just me.
I think in the sense you are asking about (IE not "morals") - A principle is a rubrick defined through observation of a series of facts and/or application of a series of concepts definitive enough to be tenetively applied to new or uncertain situations.