The 24-year-old was matched with home boxer Reece Allen-Jones, 20. Both weighed in at 78kg.
Coach Gerry Lavelle said the bout was taken at short notice but it was seen as a good chance to put Cotton’s improving form to the test.
Cotton was told to feel the first round out behind his jab, scoring points and staying out of harm’s way, and he did just that, catching Allen-Jones with some big overhand right crosses. Cotton won the first round but had to up the ante. In the second Cotton stepped up the pace and Allen-Jones was warned for consistent holding and picked up a very bloodied nose.
Cotton continued his relentless assault, clearly winning the second round.
Allen-Jones gave it everything in the third but received another warning for holding and needed another stoppage for nose repairs.
Lavelle said: “Arron finished on top and was barely out of breath at the end of a very exciting contest which tested him, especially against the very partisan home support.
“The contest was a clear lockout for young Arron as he recieved a very well-deserved unanimous points decision, resulting in his third win in a row.
“This is a young lad who got involved in anti-social behaviour in his younger days but who through amateur boxing has turned his life around in a very positive way.”