The problem is that I’ve just finished learning the 44 sounds of English and now I’m concerned about words that I know I may have pronounced wrong before I learned all 44 English sounds. Will this affect my score much, and if it does, how do I improve and fix this?
It affects partially your scoring - you can have an accent or occasionally mispronounce things (particularly common with words you only saw written and never heard them pronounced) and still achieve a high score as long as you score high on the other 3 criteria and your accent doesn't impact intelligibility
According to the public IELTS Speaking Band descriptors, these are the scores you can expect with a mild accent and occasional mispronunciation (assuming that you have good fluency, lexical resource and grammar):
8 - Is easy to understand throughout; L1 accent has minimal effect on intelligibility
7 - shows all the positive features of Band 6 and some, but not all, of the positive features of Band 8
For CEFR comparison, this puts you solidly into C1-B2 level
If your accent causes some clarity problems but you still have good articulation and grammar, your score gets reduced to the following:
6 - can generally be understood throughout, though mispronunciation of individual words or sounds reduces clarity at times
5 - shows all the positive features of Band 4 and some, but not all, of the positive features of Band 6
For CEFR, this score places you at B2-B1
If you have a very strong accent and the examiner has to ask you to repeat yourself quite a few times because they didn't understand you, even if you spoke grammatically correct English:
4 - mispronunciations are frequent and cause some difficulty for the listener
For CEFR, this will place you at A2
If you want a quick assessment, I can recommend EnglishScore, which is a free app* made by the British Council (which is one of the owners of IELTS).
*Testing is free, official traceable certificates are paid
For pronunciation improvement, the best thing is exposure. Hear native speakers talking often. One thing you can do by yourself is get a stretch of audio by a native speaker and the written transcript (e.g. audiobook + book, movie + script, etc.) and try to copy the way the native speaker says the words. If possible, record yourself and listen back to understand where you need to improve.
Another thing is to get feedback from a native speaker or an English teacher - be intentional about what you want to achieve, and let them know, so you can make the most out of your session