Student pilot reported during their first solo they taxied onto the runway without a clearance; causing a landing aircraft to go around

Narrative

On the morning of Day 0 I was to conduct my first solo flight here at the flight school under my instructor. After a few laps in the traffic pattern; I did a full stop; dropped my instructor off at the maintenance hanger and then continued on my engine run up as well as my taxiing to the hold short line of runway XX at [taxiway] 1. I contacted ZZZ Tower and expressed that I was ready for departure; in response; they gave me the instruction of hold short of the runway. I read back the instructions correctly along with ending my call with 'student pilot solo'. I cannot express as to why or how it came to be; but I took the active runway as I subconsciously determined the call was a 'line up and wait' call. After waiting on the active runway; for I believe 20-25 seconds I scanned my surroundings and knew something was wrong. Shortly after; I heard a call from the arriving traffic on base that they were doing a go-around. After a short delay; ZZZ tower cleared me for takeoff and I continue the flight like normal. At the time; I wholeheartedly believed that I was given a lineup and wait call so I felt as though that this was a miscommunication error with ZZZ Tower. I communicated saying that I was on the active runway waiting for the clearance to takeoff. After listening back; the only person I have to blame is myself as I was the one who did not follow directions. I am unsure as to how I had interpreted the call as such. It was not from lack of vetting from my instructor; it was impulsive actions from me; the student pilot.