Hi, I usually play the electric guitar but i plan on learning few acoustic ones too. I've started learning Canon in D but I'm only picking with my thumb, pointing finger, and my middle finger. Is this something really bad i need to change right away? or is it nothing bad and i can just keep it at that?
Its not TERRIBLY bad.. When I started guitar, I learnt classical and its prob best to play with all if you can, its hard to get used to if youv played other music before.. I havnt played classical in a while and in a class now I have to again lol. Oh well.
So try getting all or leave out Finger 4 (Pinky) for a while then try adding it in??
It's perfectly fine, provided you're not tucking in your other fingers or something. Just keep the spares out where you can use them easily should the situation arise.

Using the ring/pinky fingers might seem awkward at first, but as you incorporate them more often, it'll become more comfortable and feel more natural.
Quote by HorizonShadow
Just eat the headstock.

That'll make you look mad.
Proceed with confidence. The vast majority right hand of technical demands can be achieved using the three digits of the 'upper hand" (thumb, index and middle).
In fact, there is a fine tradition and good argument for relying upon them in most situations.
However, ring finger training ought not be neglected if you are serious about advancing classical technique and repertoire.
Requirement for the use of the "pinky" is so extremely rare that it can be regarded as a device for the musical masochist or freaks such as Stefan Rak (bless him).
A more important concern for the beginner is correct hand position and the plucking/striking action of fingers.