Heal" and "heel" define ever so different concepts and this explains why it is so important that you don't confuse them. If you use "heel" instead of "heal", or vice versa, they will certainly be major misspellings, even if they are spelled so similarly.
Plus, anyway, these are elementary English words that any English user must know, and remembering their definitions is not difficult at all. You only have to clearly understand once what each word means, and confusing them will not represent a problem for you anymore.
Heal vs. Heel
The major difference between "heal" and "heel", as well as the best way to remember what each refers to, is that "heal" is a verb, while "heel" is a noun.
When do we use "heal"?
"Heal" is a verb, referring to the action of making something healthy again, whether it's a wound, a broken bone etc. It defines the process of repairing something broken when it comes to a living organism. Figuratively, the word can also be used referring to forgetting, forgiving or passing over a moment/period of sufferance or pain.
Example 1: I will let my headache heal naturally because I don't want to take any pills. - "heal" refers to the action of making something healthy and painless again.
Example 2: I try to meditate, sleep and find my inner peace in order to heal my soul. - used with a figurate sense, "heal" can refer to bringing back peace to one's soul or mind.
When do we use "heel"?
"Heel" is a noun and it can either define a body part - the back part of the foot -, or that part of the shoe that is situated right under the heel.
Example 1: My shoes were uncomfortable, so I have a really bad pain in my heel right now. - "heel" is that body part situated in the back part of the foot.
Example 2: She loves wearing high heels. - "heel" can also refer to the part of the shoe situated under the heel.
The easiest way to remember the meanings of these words is to keep in mind that "heal" is a verb, referring to the way something gets healthy again, while "heel" is a shoe component or a body part, situated at the back of the foot.