What you describe is called a biceps tendon rupture which is a very serious injury. There are two types: at the shoulder and, far more serious, at the elbow called a distal biceps tendon rupture. I got the later one during aikido on June 10th 20011, had surgery on June 25th 2011. Stelios, even if you think your arm is kind of ok, it is a very serious injury that needs utmost care and this care has to come three weeks post injury because after that, it becomes a far more delicate surgery most probably involving a graph tendon from a cadaver or from your own body from somewhere else. Very sorry for spooking you, but this is what this injury is about and it is huge mental shock to me. Muscle and/or tendon tears are very difficult to heal and almost always need instant surgery to repair otherwise, ie if you choose not to do surgery, you lose a very big amount of strength and range of motion.... for life probably, really not wanting to scare you.
It will be at least 6 months at least before you can fairly consider returning to aikido. And at that point you need to take it from the ground up very slowly gradually up to another 6 months. Look Stelios, aikido is a HUGE part of my life and it has been a very depressive blow to me to understand the true nature of this injury but I extensively researched about it online, and believe me we need all range of motion to the arm for aikido as we supinate, pronate and extent in almost all our movements whether uke or nage.
And to have the best chances, and there are many, you need to heal it properly and over a VERY long time. And despite my depression, I decided to accept this very fact and we will also need extensive good quality physio therapy. I have read about powerlifters who followed this regimen with good nutrition and supplements and went on to lift more than they were pre-injury.
I suggest, like I intend to do, after three months or so, depending on the recovery, to start going at the dojo but, and after agreeing with sensei of course, on my own on the side to just do tai sabaki, stretching, soft rolls back and forth, etc. till i tire for a couple of months, then, at around six months, to start practice gradually from there very slowly, again!!!!, and increase to higher intensity.
Actually i am a lot more concerned about being uke, as most movements like kotegaishi, nikkyo, sankyo, shihonage involve some strong twisting and/or extending at some point of the technique that will eventually put a considerable strain on the repaired tendon which is why it will take a very long time I guess though i am very optimistic, if my recovery doesn't meet very possible complications, that i will be a much stronger aikidoka and hopefully take my nidan test by January 2012 God willing. Can you please give me your email address so we can maybe exchange and share progress, updates, etc. which is of immense help for the mental challenge with this kind of injury while still an aikidoka at the core. mine is: email@example.com
Domo arigato Stelios san